Hydraulic windshield wiper motor and system



Dec. 31, 1963 J. E. THRAP HYDRAULIC WINDSHIELD WIPER MOTOR AND SYSTEMFiled June 20, 1961 Dec. 31, 196; J. E. 'rl-IRAP 3,115,662

HYDRAULIC wINnsHIELD wIPER MOTOR AND SYSTEM Filed June 20, 1961 2Sheets-Sheet 2 United States Patent O 3,115,662 HYDRAULIC WENDSHELDWIPER MUTR AND SYSTEM John E. Thrap, Columbus, Gino, assigner toThompson Ramo Wooldridge Inc., Cleveland, Ghia, a corporation of OhioFiled June 2d, 1961, Ser. No. 113,298 Claims. (Cl. IS-ZStLI) Thisinvention relates to a motor and system for a Windshield wiper or thelike and more particularly to a windshield wiper system for automotiveuse or the like Wh1ch has no rigid mechanical linkage between the rightand left-hand wiper blades.

In a conventional windshield wiper system, a rigd mechanical linkagejoins the right and left-hand wiper blades on the windshield. However,this construction requires close tolerances in manufacture and issubject to frequent mechanical failure and misalignment. The presentinvention overcomes these difficulties by providing a hydraulic linkagebetween a master motor unit operating one of the wipers and a slavemechanism operating the other of the wipers and which is controlled bythe action of the master motor unit. Fluid is supplied to the systemunder pressure by means of a power steering pump, engine oil pump or anyother suitable pumping mechanism, and the master motor unit includes aspool valve which in one position directs pressurized luid to move asecond valve so that the pressurized fluid may pass to the slavemechanism. The so-called slave mechanism has a piston which operates thewiper thereof by a rack and pinion action when Huid is thus introducedthereto and the piston in turn then pressurizes a second pistonassociated with the master motor unit to operate the Wiper thereofthrough similar rack and pinion means. The second piston during thecourse of its movement contacts a linkage element slidably retainedtherein to move the spool valve in the master motor unit to a secondposition wherein pressurized fluid acts upon the second valve to causethe second valve to prevent passage of uid to the slave mechanism and totransmit fluid pressure to the second piston to move it in the reversedirection so that the linkage therein returns the spool valve to thefirst mentioned position thereof. The reverse movement of the secondpiston, of course, turns the Wiper thereon in a reverse direction ofangular movement, and the first mentioned piston is pressurized throughthe hydraulic linkage by the said reverse movement of the second pistonso that it also reciprocates to move its wiper in the reverse directionof angular rotation, whereby a cycle of movement for the wipers iscompleted. In will thus be appreciated that a continuous wiping actionmay be achieved without any rigid mechanical linkage such as hasheretofore been required.

In order to place the wipers in a park position, one of the conduitsleading from the spool valve to the sec-` ond valve is provided with aturn valve which maintains the said conduit open during movement of thewipers but closes the conduit and communicates the source of pressure tothe second valve in a manner which effects the reverse movement abovedescribed but which maintains the second valve in the position foreffecting the reverse movement so that further movement is prevented. Atthe completion of this reverse movement, of course, the blades willgenerally be disposed so that they extend toward one another.

The pressurized lluid introduced into the master motor unit as describedis pumped to the source of fluid by the piston which is linked to thespool valve. To accommodate expansion and contraction of fluid when theWipers are in the park position, however, a reservoir ice Z chamber isformed in the slave unit which is similar in function to the mastercylinder of an automobile.

Accordingly, it is an object of the present invention to provide ahydraulic windshield wiper motor and system.

Another object of the invention is to provide a motor and system asdescribed which eliminates the previously required mechanical linkagebetween the respective wiper blades.

Another object of the invention is to provide a device as describedwherein the blades are synchronized hydraulically and actuated bypressurized fluid from a source such as a power steering pump, engineoil pump, or the like.

Another object of the invention is to provide a device as describedwhich affords continuous reciprocation of the blades when a turn valveis moved to one position and which places the blades in a park positionupon rotation of the turn valve to another position.

Another object of the invention is to provide a device as describedhaving a master motor unit and a slave motor unit dependent upon theoperation of valves in the master motor unit which in turn arecontrolled by the pressurized iiuid and the movement of a pistonassociated with the master motor unit.

Yet another object of the invention is to provide a device as describedwhich is simple and reliable and which may be used in a variety ofsituations where synchronized action of elements such as windshieldwipers is required.

Other objects and advantages of the invention will become apparent asthe description proceeds in accordance with the drawings in which:

FIGURE 1 is a schematic view of a hydraulic windshield wiper motoraccording to the present invention in a position such as to initiateoutward sweep of the wiper blades;

FIGURE 2 is a view of the motor showing the wiper blades midway in theoutward sweep and a wiper actuating piston for the master motor unit ininitial contact with a link controlling a spool valve in the mastermotor unit;

FIGURE 3 is a corresponding View showing the wiper blades at theconclusion of their outward sweep and with the motor in a position suchas to initiate their inward sweep; and

FIGURE 4 is a view showing the motor and wiper blades in park position.

Referring now to the drawings, a Windshield wiper motor it? is shownaccording to the present invention, which operates hydraulically so thata pair of wiper blades 11 and 12 are synchronized Without any mechanicallinkage being required. The motor 10 includes a master motor unit 14which is in series circuit with a slave motor unit I6 through ahydraulic circuit which includes a conduit I8 communicating conduits 2@and 22 in the master motor unit with a chamber 24 in the slave motorunit, and a conduit 26 communicating a chamber 23 in the slave unit witha chamber 36 forming a part of the master motor unit.

The blades 11 and l2 are preferably operated by rack and pinion meansand thus a piston 32 is reciprocably mounted in a bore in a casing 33forming the chambers 24 and 28 in the unit 16, and defines a rack 34meshing with a pinion 36 for the blade 12. Likewise, a piston 38 isreciprocably mounted in a bore in a casing 40 which forms the chamber30, the casing 46 preferably being secured in any suitable manner to ablock 42 for the master motor unit 14 while the casing 33 for the sleevemotor unit 16 is entirely separate and spaced from the unit I4. Thepiston 33 also forms a rack 44 meshing with a pinion 46 for the blade11.

The conduit 26 thus hydraulically links the pistons 32 and 38 forsynchronized reciprocation, in cooperation with the conduit 26 and aconduit 47 leading from conduits 48 and 49 in the block 42 into theother end of the bore in casing 40. In order to achieve this result,hydraulic luid is supplied to the master motor unit I4 by means of apower steering pump, engine oil pump or any other available pumpingmechanism (not shown) through a conduit 5i?. The conduit 5@ enters achamber 52 in the block 42, which may be lined for a major portion ofits length by a suitably apertured plastic liner 5d or the like.

To control the operation of the device, a spool valve 56 is reciprocablymounted within the chamber 52 and the liner 54 and defines a centralannular recess forming a chamber 53 which is in continuous communicationwith the conduit 50.

The conduit IS is thus intermittently communicated with the chamber 5Sand the conduit 50 by means of a chamber 6@ which receives a secondvalve 62 having three axially spaced lands 64, 66 and 68 mounted on astem '7d which projects outwardly beyond the lands 64 and 68. The valve62 reciprocates in a liner 72 for the chamber 6). In the position ofFIGURE l, the valve 62 aords communication between the Conduit 22 andthe chamber 53 via a conduit 74 which enters an intermediate portion ofthe chamber 6) so that it is continuously in communication therewith.Accordingly, the iiuid from the conduit Si) is passed through thechamber 5S, conduit 7d, chamber 6) and conduit 22, into the conduit I,thereby to move the piston 32 to the left as the result of pressureintroduced into the chamber 2dfrom the conduit IS. Simultaneously, thechamber 2% is reduced to pressurize piston 38 and move it to the ri ht,by passage of hydraulic uid through the conduit 26 into the chamber 3?.Accordingly, an outward sweep of the blades is achieved.

It will also be seen that in the position of FIGURE l, pressurized uidis introduced to the left-hand side of the valve 62 via a conduit 76communicating at that time with the chamber 58. However, a conduit 7S issealed from the pressurized chamber 5S by a land 8@ on the spool valveS6. The conduit 78 is in continuous communication with the right-handside of the chamber 69 and, as hereinafter noted, a turn valve 32 isrotatably mounted in the block 42 to form a portion of the conduit 78,in the operative condition of the motor lil.

Referring to FIGURE 3, reverse movement of the blades Il and I2 isachieved by movement of the valve 56 to the right to cause a land Sdthereon to seal the conduit 76 from the pressurized chamber 53. In thisposition of the spool valve S6, the conduit 73 communicates with thechamber SS to pressurize the right-hand side of the valve 62. Thus thevalve 62 is moved to a left-hand position such that the chamber 6i)communicates with the conduit 49 via the area 86 between the lands 66and 63 which is in continuous communication with the conduit '74 andchamber 55. Thereby, the piston 38 is moved to the left and the chamber3i) is reduced to transmit hydraulic fluid through the conduit 26 to thechamber 2S, simultaneously moving the piston 32 to the right. Asindicated, this movement of the pistons 38 and 32 eifects an inwardsweep of the blades lll and l2.

It is therefore apparent that the spool valve S6 controls the secondvalve 62 so as to pass iiuid alternately through the right-hand lowerconduit 18 or through the left-hand lower conduit 47.

In order to control the movement of the spool valve 56, the piston 3S isprovided with an internal elongated chamber SS in which is reciprocablyreceived a linkage head 90 whose length is less than the length of thechamber S8 by a predetermined amount such as to afford a lost motion andtime delay action. The linkage head 96 has a stem 92 extending outwardlythrough a right-land opening 4- in the piston 38. The stem 92 is fixedlyconnected in coaxial relation to the piston 56, as by stop elements 96and 98 at each end of the spool valve. The piston 38 has an insert orplug itl@ therein which forms an end wall 162 for the chamber 83.

At the position of FIGURE l, which represents the beginning of theoutward sweep of the wiper blades l1 and I2, it will be seen that thelinkage head 9@ is spaced from the wall M92. As the outward sweepprogresses, however, the end wall 162 contacts the head 9i), as seen inFIGURE 2, and moves it and the spool valve 56 to the right, and to theposition shown in FIGURE 3. Thus it will be appreciated that a fullextent of movement of the pistons 38 and 32 to complete the outwardsweep of the wiper blades lll and l2 is provided, but the movement or"the head 99, stern 92 and spool valve 56 is less than the movement ofthe piston 33 and is just sudicient to change the position of the spoolvalve so as to close the conduit 76 from chamber 5S and open the conduit78 to the chamber 58.

Conversely, a lost motion and time delay action is afforded by themovement of the piston 38 to the left, from the position shown in FIGURE3 as hereinabove described. Thus a wall or surface 104 is formed in thepiston 33 opposite the wall 102 and which engages the head @ti of thelinkage after a predetermined amount 0f movement to the left of the saidpiston 38, thereby to draw the spool valve 56 back into the position ofFIG- URE l from the position thereof shown in FIGURE 3.

Accordingly, the spool valve 56 will have a shorter stroke than thepiston 38 and the piston 32 will have a stroke equal to that of thepiston 38 and will reciprocate substantially in phase and simultaneouslytherewith for effecting synchronized cycling of the blades 11 and 12.

It will be appreciated that the time delay mechanism described isafforded so that pressure tending to reverse the direction of thepistons is not released until the full movement of the pistons in agiven direction has been achieved. However, by proper calibration of theconduits 76 and 78 with the spool valve 56, an integral connectionbetween the said spool valve and the piston 38 may be encompassed withinthe scope of the invention.

When the piston 33 is moved to the right as seen in FIGURE 2, fluid willbe passed from the right-hand chamber 196 in the bore in casing 4i),through the conduit 47 and upwardly through the conduit 48 tocommunicate with a conduit 163 which enters the right-hand end of thechamber 52 and with a conduit or return line lltl leading from thechamber 52 to return the fluid to a reservoir or the like for thepumping system. The right-hand position of the valve 62 which affordsthis uid release is eiected by pressure introduced from the conduit Siland chamber 58 through the conduit 76 to the left-hand portion T112 ofthe chamber 60. At this time the conduit 49 and conduit 47 are sealedfrom pressurized fluid by the land 66. When the valve 62 is in theposition of FIGURE 3 for introducing iiuid through the conduits 47 andi9 to the chamber 106, the land 66 seals off the conduit 4S to preventcommunication thereof with the return line llt).

Conversely, during the movement of the piston 32 to the right from theposition thereof shown in FIGURE 3, fluid is passed from the chamber 2dthrough the conduit 1S and thence through the conduit 20 into thechamber 6@ to communicate through the conduit 108 and chamber 52 withthe return line liti. However, when the conduit I8 is pressurized viathe conduits 50 and 22, as shown in FIGURE 6, the land 64 seals olf theconduit 2t) from the return line 110.

The spool valve S6 is designed to accommodate pressure in the chamber 6@effected by the reciprocation of the second valve 62. To this end,annular recesses 114 and M6 are formed in the lands 84 and 80respectively and these recesses in turn communicate with radial passageslid and 126 connected by a central axial bore 122 within the spool valveS6 which receives the stem 92. The recesses 114 and M6 are thus spacedaxially so that in the position of FIGURE 1 the recess 116 communicateswith the passage or conduit 7? while the recess 114 is sealed by theliner 5a and in the position of FIGURE 3 the recess M4 communicates withthe conduit 76 and the recess 116 is sealed by the liner 54.Accordingly, when pressure is introduced at the left-hand side of theValve 62, as shown in FIGURE 1, the passage 78 will relieve the pressureat the right-hand side of the chamber 60 via passage 120; and when theright-hand side of the valve 62 is pressurized, as shown in FIGURE 3,the conduit 76 Will relieve the left-hand side 112 of the chamber 69 viathe recess 114 and the passage 118. The passages 118 and 129 will thusalternately receive the excess fluid and the bore 122 may in turn havesome communication with the chamber 52 and with the return line 110.

In order to position the motor in park condition, the valve 82 is turnedso that a passage 124 therein is placed in register with a conduit 126which communicates with the source of pressurized fluid. The valve 82has an auxiliary passage 128 communicating with the passage 124 at anangle such as to register with the lower portion of the conduit 7S atsuch time. The passage 124- in the operative condition of the motorforms a portion of the conduit 78. When the turn valve has its passage124 in register With the conduit 126 as described, therefore, theright-hand side of the chamber 60 is pressurized to overcome thetendency of the valve 62 to move to the right from the position ofFIGURE 4.

When the pistons 3S and 32 have moved outwardly to the position ofFIGURE l from the position of FIG- URE 3 as the result of the pressureimparted through the conduit 47, the spool valve S6 will also have beenreturned to the position of FIGURE 1 as hereinabove set forth. Thispositioning of the spool valve 56 will open the conduit 76 to the sourceof pressure in conduit 50 and thus will pressurize the left-hand side ofthe charnber 60 indicated by numeral 112. The pressure introducedthrough the conduit 124 Will, as stated, overcome the pressure at thearea 112 to maintain the land 68 in sealing relationship to the passage22 and prevent repressurizing of the conduit 1S. Thus the piston 32willnot move to the left and the piston 38 will not return to the rightso that a park condition for the motor will be maintained as seen inFIGURE 4.

Since the unit 16 is a slave mechanism depending on the action of themaster motor unit 14, the chambers 2S and 11?@ and the conduit 26 form acompletely sealed enclosure and the respective pistons 32 and 38 areprovided with O rings 130 and 132 respectively. The fluid employed mayundergo some expansion or contraction depending on temperatureconditions and the like when the motor 1@ is in the par condition andtherefore a reservoir chamber 134 is formed in the casing 44 for theunit 16, which communicates through a passage 136 with the bore in whichthe piston 32 is received. A vent 138 may be formed for the chamber134ias by a plug 14) threaded in the casing 33. This reservoir is thussimilar in function to the master cylinder of an automobile.

The bore for the piston 38 is sealed from the chamber 52 for the spoolvalve 56 by means of a disk or the like 142 which may be secured in arecess 144 in the casing 40 so as to abut the block 42 of the unit 14,although various types of divider constructions may be utilized withinthe scope of the invention and in fact the casing di) may be formedseparately from the block 42. The disk 142 retains an inner O ring 146sealing the stem 92 during its reciprocable movement. The chamber 60 mayalso be formed as a bore sealed by a plug or the like 148 to provide thedesired length for the chamber in relation to the valve 62. Similarly,the bore for the piston 32 may be closed olf by an end Wall 150 on thecasing 33 which is apertured to receive the conduit 18.

There has thus been provided a windshield wiper system having a minimumof moving parts and which is adapted to operate effectively overextended periods of time. The elimination of a mechanical link betweenthe respective wiper blades affords a simplified construction whichobviates the need for close tolerances, and also prevents undue stressin the event that one of the wiper blades inadvertently is restrained,with consequent elimination of misalignment such as has occurred withpreviously available wipers. It will also be evident that the system isapplicable to a Wide range of installations requiring synchronizedmovement of individual parts.

Although I have herein set forth and described my invention with respectto certain specic principles and details thereof, it will be understoodby those skilled in the art that the invention is not limited theretobut is to be construed in accordance with the spirit and scope of thehereunto appended claims.

I claim as my invention:

1. A Windshield wiper comprising a pair of housings each having achamber, a piston reciprocably received in each of said chambers, eachof said pistons forming a rack, a pinion journaled in each of saidhousings in meshing relation with the piston therein, a wiper blade oneach of said pinions, a conduit connecting a corresponding end of eachof said chambers, hydraulic fluid in said conduit, each of said chambershaving a conduit entering the other end thereof, a housing having apairv of chambers therein, said last-named conduits each having abifurcated end entering one of said pair of chambers, a source ofpressurized uid entering the other of said pair of chambers, a returnline leading from said other of said pair of chambers, `a spool valve insaid other of said pair of chambers, means linking said spool valve Withone of said pistons for reciprocation therewith, a pair of conduitsleading from said other of said pair of chambers to opposite ends ofsaid one of said pair of chambers, and positioned to be alternatelyclosed by reciprocation of said spool valve, a valve in said one of saidpair of chambers reciprocated by uid from said source of pressurizedfluid introduced into said one of said pair of chambers alternatelythrough said pair of conduits, a conduit continuously communicating saidone of said pair of chambers with said source of pressurized fluid and aconduit continuously communicating said one of said pair or" chamberswith said return line, said valve in said one of said chambers having aplurality of lands spaced axially to alternately communicate saidbifurcated conduits with said source of pressurized fluid and with saidreturn line through alternate branches of the bifurcations so that oneof said bifurcated conduits communicates with Ysaid source ofpressurized fluid when the other of said bifurcated conduitscommunicates with said return line.

2. A windshield wiper comprising a pair of housings each having achamber, a piston reciprocably received in each of said chambers, eachof said pistons forming a rack, a pinion journaled in each of saidhousings in meshing relation with the piston therein, a Wiper blade oneach of said pinions, a conduit connecting a corresponding end of eachof said chambers, hydraulic uid in said conduit, each of said chambershaving a conduit entering the other end thereof, a housing having a pairof chambers therein, said last-named conduits each having a bifurcatedend entering one of said pair of chambers, a source of pressurized fluidentering the other of said pair of chambers, a return line leading fromsaid other of said pair of chambers, a spool valve in said other of saidpair of chambers, means linking said spool valve with one of saidpistons for reciprocation therewith, a pair of conduits leading fromsaid other of said pair of chambers to opposite ends of said one of saidpair of chambers, and positioned to be alternately closed byreciprocation of said spool valve, a valve in said one of said pair ofchambers reciprocated by fluid from said source of pressurized fluidintroduced into said one of said pair of chambers alternately throughsaid pair of conduits, a conduit continuously communicating said one ofsaid pair of chambers with said source of pressurized liuid, a conduitcontinuously communicating said one of said pair of chambers with saidreturn line, said valve in s,115,ee2

said one of said chambers having a plurality of lands spaced axially toalternately communicate said bifurcated conduits With said source ofpressurized fluid and with said return line through alternate branchesof the bifurcations so that one of said bifurcated conduits communicateswith said source of pressurized huid when the other of said bifurcatedconduits communicates with said return line, a turn valve in one of saidpair of conduits and a second source of pressurized fluid leading tosaid turn valve, said turn valve opening said one of said pair ofconduits between said pair of chambers while sealing said second sourceof pressurized fluid therefrom in one position thereof, and closing saidone of said pair of conduits between said pair of chambers While openingsaid second source of pressurized uid to said one of said pair otchambers in another position thereof.

3. A synchronized cycling device comprising a pair of housings eachhaving a chamber, a piston reciprocably received in each of saidchambers, a conduit connecting one end of each of said chambers,hydraulic fluid in said conduit, each of said chambers having a conduitentering the other end thereof, a housing having a pair of chamberstherein, said last-named conduits each having a bifurcated end enteringone of said pair of chambers, a Source of pressurized fluid entering theother oi said pair of chambers, a return line leading from said other ofsaid pair of chambers, a spool valve in said other of said pair ofchambers, means linking said spool valve with one of said pistons forreciprocation therewith, a pair of conduits leading from said other ofsaid pair of chambers to opposite ends of said one of said pair ofchambers, and positioned to be alternately closed by reciprocation ofsaid spool valve, a valve in said one of said pair of chambersreciprocated by fluid from said source of pressurized fluid introducedinto said one of said pair of chambers alternately through said pair ofconduits, a conduit continuously communicating said one of said pair ofchambers with said source of pressurized liuid and a conduitcontinuously communicating said one of said pair of chambers with saidreturn line, said valve in said one of said chambers having a pluralityof lands spaced axially to alternately communicate said bifurcatedconduits with said source of pressurized fluid and With said return linethrough alternate branches of the bifurcations so that one of saidbifuracted conduits communicates with said source of pressurized fluidwhen the other of said bifurcated conduits communicates with said returnline.

4. A synchronized cycling device comprising a pair of housings eachhaving a chamber, a piston reciprocably received in each of saidchambers, a conduit connecting one end of each of said chambers,hydraulic fiuid in said conduit, each of said chambers having a conduitentering the other end thereof, a housing having a pair of chamberstherein, said last-named conduits each having a bifurcated end enteringone of said pair of chambers, a spurce of pressurized iluid entering theother of said pair of chambers, a return line leading from said other ofsaid pair of chambers, a spool valve in said other of said pair ofchambers, means linking said spool valve With one of said pistons forreciprocation therewith, a pair of conduits leading from said other ofsaid pair of chambers to opposite ends of said one of said pair ofchambers, and positioned to be alternately closed by reciprocation ofsaid spool valve, a valve in said one of said pair of chambersreciprocated by fluid from said source of pressurized fluid introducedinto said one of said pair of chambers alternately through said pair ofconduits, a conduit continuously communicating said one of said pair ofchambers With said source of pressurized liuid, a conduit continuouslycommunicating said one of said pair of chambers with said return line,said valve in said one of said chambers having a plurality of landsspaced axially to alternately communicate said bifurcated conduits withsaid source of pressurized fluid and with said return line throughalternate branches of the bifurcations so that one of said bifurcatedconduits communicates with said source of pressurized liuid when theother of said bifurcated conduits communicates with said return line andmeans for selectively pressurizing and depressurizing one end of saidone of said pair of chambers to prevent further reciprocation of thevalve therein and further reciprocation of said pistons and said spoolValve and to initiate reciprocation of said valve therein said pistonsand said spool valve as desired.

5. A device for actuating elements in synchronized cycles comprising apair of housings each forming a chamber therein, a piston reciprocablydisposed in each of said chambers in substantially sealing relationshipthereto, a huid filled conduit intercommunicating one end of each ofsaid chambers, a housing having first and second chamers therein, avalve reciprocably disposed in each of said first and second chambers,means linking the valve in said first chamber with one of said pistonsto reciprocate the vaive by reciprocation of the piston, first conduitmeans connecting the other end of each of said chambers receiving saidpistons with said second chamber, a source of pressurized fluidcommunicating with said first chamber, means relieving pressurized fluidfrom said first chamber and second conduit means connecting said firstand second chambers, said valves having sealing surfaces and said secondconduit means cooperating with said sealing surfaces to reciprocate saidvalve in said second chamber in response to reciprocation of said valvein said first chamber, said first conduit means cooperating with thesurfaces on said valve in said second chamber to alternately communicatesaid source of fluid pressure with the other ends of said chambersreceiving said pistons while successively alternately communicating saidmeans relieving pressurized fluid with the other ends of said chambersreceiving said pistons.

6, A device for actuating elements in synchronized cycles comprising apair of housings each forming a chamber therein, a piston reciprocablydisposed in each of said chambers in substantially sealing relationshipthereto, a fluid filled conduit intercommunicating one end of each ofsaid chambers, a housing having first and second chambers therein, avalve reciprocably disposed in each of said first and second chambers,means linking the valve in said first chamber With one of said pistonsto reciprocate the valve by reciprocation of the piston, first conduitmeans connecting the other end of each of said chambers receiving saidpistons with said second chamber, a source of pressurized uidcomunicating with said first chamber, means relieving pressurized fluidfrom said first chamber and second conduit means connecting said firstand second chambers, said valves having sealing surfaces and said secondconduit means cooperating with said sealing surfaces to reciprocate saidvalve in said Second chamber in response to reciprocation of said valvein said first chamber, said rst conduit means cooperating with thesurfaces on said Valves toalternately communicate said source of fluidpressure with said other end of one of said chambers receiving saidpistons while simultaneously communicating said means relievingpressurized fluid with said other end of the other of said chambersreceiving said pistons and communicate said means relieving ressurizedfluid with said other end of one of said chambers receiving said pistonsWhile simultaneously communicating said means relieving pressurizedfluid with said other end of the other of said chambers receiving saidpistons and valve means selectively introducing fluid pressure into andsealing fiuid pressure from said second charnber to preventreciprocation of said valve in said second chamber and thereby toprevent reciprocation of said pistons and said valve in said firstchamber and to initiate rcciprocation of said valves and pistons asdesired.

7. A synchron-ized cycling device comprising a pair of housings, a firstchamber in one of said housings, a second chtunber in the other of saidhousings, a piston reciprocably received in each of said chambers, afluid filled conduit intercommunicating one end of cach of saidchambers, a third housing having third and fourth chambers therein, afirst valve in said third chamber, a second valve in said fourthchamber, first conduit means connecting said fourth chamber lwith theother ends of said first and second chambers, a source of pressurizedfluid, second conduit means connecting said `source of pre-ssurized uidwith said third chamber, third conduit means connect-ing said source ofpressurized fluid with said fourth chamber, fourth conduit meansconnecting said third chamber with opposite ends of said fourth chamber,fluid release means, fifth conduit means connecting said third andfourth chambers With said fluid release means and means reciprocatingsaid first valve as 'a function of the reciprocation of one of saidpistons, said Ifirst valve controlling said third conduit means toreciprocate said second valve and -said second valve controlling saidfirst conduit means to alternately communicate the other ends of saidfirst and second chambers with said third conduit means and said sourceof pressurized fluid yand with said iifth conduit means and said fluidrelease means, said other end of -said rst and second chamberscommunicating with one of said third and fifth conduit means when theother end of the other of said firs-t and second chambers communicateswith the other of said third and fifth conduit means.

`8. A device for actuating elements such as windshield Wipers and thelike comprising a housing having first and second ychambers therein, afirst valve in said first chamber, a second valve in said secondchamber, a pair of piston means, hydraulic means linking said pistonme-ans for mutual reciprocation, means reciprocating said first valve asa function of the reciprocation of |one of said piston means, said rstvalve being a spool valve, a conduit leading -from each end of saidsecond chamber to said first chamber each llocated to be closedalternately from said source of pressurized fiuid yby said first valveto lreciprocate said second valve, a conduit for each of said pistonmeans, leading to said second .chamber and each controlled by saidsecond valve to alternately communicate said piston means with saidsource of pressurized fluid and to reciprocate said piston means incooperation with said hydraulic means, and conduit means for releasingfluid from said chambers, said second valve alternately communicatingsaid conduits for said piston means with said conduit means forreleasing fluid from said chambers, a pair of passages in said firstvalve each communicating with one of said conduits leading from the endsof said second chamber when said one o-f said conduits is closed fromsaid source of pressurized iiuid and a passage in said first valve`communicating said pair of passages 'with said :conduit means forreleasing fluid from said chambers whereby to alternately relievepressure at the ends of said second chamber during reciprocation of saidsecond valve.

9. A device for :actuating elements such as Windshield wipers and `thelike comprising a housing havin-g first and second chambers, a firstspool valve in said first chamber, a second vaive in said secondchamber, a pair of housings each having a chamber and a pistonreciprocably received therein, one of said pistons being coaxial withsaid spool valve, a fiuid iii-led conduit communicating between one endof each of said chambers for said pistons, a conduit communicatinganother end of each of said chambers lfor said pistons with said secondchamber, a source Iof pressurized fluid leading to said first chamberand said second chamber, said one Iof said pistons having a pair ofaxially spaced stops, a link having a head engaged by alternate stops ofsaid axially spaced stops during reciprocation of said one of saidpistons and a ste-m connected to said spool valve and conduit ineanscooperating with said spool valve to alternately communicate said source`of pressurized fluid with opposite ends of said second chamber, saidsecond valve being configured to reciprocate in resonse to the alternatepressurization of said ends of said second chamber and to alternatelycommunicate said conduits for the other ends of said chambers for saidpistons with said source of pressurized iiuid, said link affording alost motion action such as to reciprocate said spool valve with a timedelay from initial movement of said one of said pistons in one directionor the other whereby Ito pressurize said conduits for the other ends ofsaid chambers for said pistons substantially upon completion of `thestroke of the pistons in the -direction tov/ard said other ends of saidchambers for said pistons.

10. A synchronized cycling device comprising a pair of housings eachhaving a chamber, a piston reciprocably received .in each of saidchambers, each of said pistons forming a rack, a pinion journaled ineach of said housings in meshing relation with the pinion therein, aconduit connecting one end of each of said chambers, hydratrlic fluid insaid conduit, each of said chambers having a conduit entering the otherend thereof, a .housing having 4a pair of chambers therein, saidylast-named conduits each having a bifurcated end entering one of saidpair 'of chambers, a source of pressurized iiuid entering the other ofsaid pressurized chambers, a return line leading from said other of saidpair of chambers, a spool valive in said other of said pair of chambers,means linking said spool valve with one of said pistons forreciprocation therewith, a pair of conduits leading from said other ofsaid pair of chmibers to opposite ends of said one of said pair ofchambers, and positioned to be alternately closed by reciprocation ofsaid spool valve, a valve in said ione of said pair of chambersreciprocated by fluid from said source of pressurized fluid introducedinto said one of said pair of chambers alternately through said pair ofconduits, a conduit continuously communicating said one of said pair ofchambers with said source of pressurized fiuid, la conduit continuouslycommunicating said one of said pair of chambers with said return line,said valve in said one of said chambers having a plurality of landsspaced axially to alternately communicate said bifurcated conduits withsaid source of pressurized fluid and With said return line throughalternate branches of the bifurcations so that one of said biiurcatedconduits communicates with said source of pressurized iiuid when ltheother of said bifurcated conduits communicates with said return line,means for selectively pressurizing and depressurizing one end :of saidone of said pair of chambers to prevent further reciprocation of thevalve therein and further reciprocation of said pistons and said spoolvalve and to initiate reciprocation of said valve therein, said pistons.and said spool valve as desired and a reservoir in said housing Iforthe other of said pistons having a reservoir chamber therein incommunication with the chamber for said piston therein adjacent the rackon said piston Ito `compensate for chan-ges in fluid volume in saidconduit connecting said chambers for said pistons.

References Cited in the file of this patent UNITED STATES PATENTS2,516,558 Freedman et al. July 25, 1950 2,609,795 Freedman et al Sept.9, 1952 2,825,919' Horton Mar. 1l, 1958 2,830,314 Bitzer Apr. 15, 1958

1. A WINDSHIELD WIPER COMPRISING A PAIR OF HOUSINGS EACH HAVING ACHAMBER, A PISTON RECIPROCABLY RECEIVED IN EACH OF SAID CHAMBERS, EACHOF SAID PISTONS FORMING A RACK, A PINION JOURNALED IN EACH OF SAIDHOUSINGS IN MESHING RELATION WITH THE PISTON THEREIN, A WIPER BLADE ONEACH OF SAID PINIONS, A CONDUIT CONNECTING A CORRESPONDING END OF EACHOF SAID CHAMBERS, HYDRAULIC FLUID IN SAID CONDUIT, EACH OF SAID CHAMBERSHAVING A CONDUIT ENTERING THE OTHER END THEREOF, A HOUSING HAVING A PAIROF CHAMBERS THEREIN, SAID LAST-NAMED CONDUITS EACH HAVING A BIFURCATEDEND ENTERING ONE OF SAID PAIR OF CHAMBERS, A SOURCE OF PRESSURIZED FLUIDENTERING THE OTHER OF SAID PAIR OF CHAMBERS, A RETURN LINE LEADING FROMSAID OTHER OF SAID PAIR OF CHAMBERS, A SPOOL VALVE IN SAID OTHER OF SAIDPAIR OF CHAMBERS, MEANS LINKING SAID SPOOL VALVE WITH ONE OF SAIDPISTONS FOR RECIPROCATION THEREWITH, A PAIR OF CONDUITS LEADING FROMSAID OTHER OF SAID PAIR OF CHAMBERS TO OPPOSITE ENDS OF SAID ONE OF SAIDPAIR OF CHAMBERS, AND POSITIONED TO BE ALTERNATELY CLOSED BYRECIPROCATION OF SAID SPOOL VALVE, A VALVE IN SAID ONE OF SAID PAIR OFCHAMBERS RECIPROCATED BY FLUID FROM SAID SOURCE OF PRESSURIZED FLUIDINTRODUCED INTO SAID ONE OF SAID PAIR OF CHAMBERS ALTERNATELY THROUGHSAID PAIR OF CONDUITS, A CONDUIT CONTINUOUSLY COMMUNICATING SAID ONE OFSAID PAIR OF CHAMBERS WITH SAID SOURCE OF PRESSURIZED FLUID AND ACONDUIT CONTINUOUSLY COMMUNICATING SAID ONE OF SAID PAIR OF CHAMBERSWITH SAID RETURN LINE, SAID VALVE IN SAID ONE OF SAID CHAMBERS HAVING APLURALITY OF LANDS SPACED AXIALLY TO ALTERNATELY COMMUNICATE SAIDBIFURCATED CONDUITS WITH SAID SOURCE OF PRESSURIZED FLUID AND WITH SAIDRETURN LINE THROUGH ALTERNATE BRANCHES OF THE BIFURCATIONS SO THAT ONEOF SAID BIFURCATED CONDUITS COMMUNICATES WITH SAID SOURCE OF PRESSURIZEDFLUID WHEN THE OTHER OF SAID BIFURCATED CONDUITS COMMUNICATES WITH SAIDRETURN LINE.